Semiconductor devices continue to be scaled to smaller dimensions. The reduction in size of circuitry, such as capacitors in dynamic random access memory (DRAM) bit cells, has prompted a need to integrate high dielectric constant materials into the fabrication of such devices. Barium strontium titanium oxide (BST) and similar materials are high dielectric constant (high-k) materials currently being used as part of this integration scheme. However, these high-k materials may be incompatible with many commonly used electrode materials because they require high temperature anneals in oxygen or deposition at high temperatures in the presence of oxygen in order to achieve their desired electrical properties. The exposure to oxygen at high temperatures is problematic because it can result in an oxidation of the electrode. This, in turn, can produce changes in the electrical properties of the capacitor.
In order to minimize the problems associated with oxidation, materials that are resistant to oxidation at high temperatures and materials which form conductive oxides, such as platinum, iridium, palladium, ruthenium, osmium, and the like are being investigated for use in forming electrodes. However, current methods for forming electrodes using these materials are not without problems. Ruthenium is easily etched in an oxygen-containing plasma, however, one of the by-products, ruthenium oxide (RuO.sub.4), is toxic. In addition, by-products of etchants commonly used to etch conductive materials, such as halogens, have low volatilities or are unstable when etching materials such as platinum, palladium, and iridium. This creates difficulties when etching these materials, particularly as the materials become thicker to accommodate higher aspect ratio features and as the spacing between the features decreases. That is, because such by-products have low volatility, they are not easily removed from high-aspect ratio structures.
Using high powered etching conditions and alternative processes, such as ion milling, to etch the thicker material, comes at the expense of selectivity loss and trenching of underlying films, as well as the formation of veils around the etched features. Trenching of underlying films is undesirable because of the impact it can have on device performance. Veils, or sidewall polymer, present a reliability concern. Their removal is difficult and is accomplished at the expense of lost time and additional processing steps. A need therefore exists to develop alternative manufacturing methods for forming conductive electrodes that are not susceptible to problems discussed hereinabove.